(function(win,doc){
	//浏览器缩放时
	win.onresize=function(){
		change();	
	};
	change();
	function change(){
		
	//320  20px 
	//414  20px
		var oFs=doc.documentElement.clientWidth/(320/20);

		//设置根目录字体大小
		doc.documentElement.style.fontSize=oFs+'px';	
	}	
})(window,document);